Photoluminescence from GaN nanopowder: The size effect associated with the surface-to-volume ratio

Nanosized GaN powder with the average grain size changing from ∼10to∼30nm has been obtained by combustion method with some modifications and its optical properties have been investigated by photoluminescence (PL). The GaN band-gap-related PL band at ∼3.4eV and surface-related PL bands centered at ∼2.0 and ∼2.8eV have been observed for this powder. The relative intensities between observed PL bands change in favor of the surface-related PL band with the decrease of the grain size. This phenomenon has been attributed to the change in the surface-to-volume ratio.